The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Further scaling of transistors will require materials to replace silicon (Si) in transistor channels. For example, use of germanium (Ge) and silicon germanium (SiGe) film and films including type III/V materials such as gallium (Ga), arsenic (As) and indium (In) have been proposed for future generations of transistors. Material selective pattering of these advanced materials beyond 7 nm node is challenging. These materials have a very low chemical resistance especially to oxidation. Oxides of these materials are usually water soluble, which poses additional challenges for wet chemical approaches.
For example, Ge/SiGe nanowires may be used in some applications. The SiGe film (typically with 50-75% Ge) needs to be etched selectively relative to the Ge film. However, the Ge film has a much lower chemical resistance towards oxidizing solutions than the SiGe film. Traditional wet chemistries are based on oxidizing and dissolution steps. Therefore, the oxidation step poses a significant limitation since the Ge film is etched significantly faster than the SiGe film.